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The coefficient of `x^70` in the product `(x-1)(x^2-2)(x^3-3)....(x^12-12)` isA. `4`B. `6`C. `8`D. `12` |
Answer» Correct Answer - A `(a)` The highest power of `x=1+2+3+….+12=78` to get coefficient of `x^(70)`, we have to omit the factors containing `x^(8)` `(1)` Product of the constant terms of `(x-1)(x^(7)-7)=7` `(2)` Product of the constant terms of `(x^(2)-2)(x^(6)-6)=12` `(3)` Product of the constant terms of `(x^(3)-3)(x^(5)-5)=15` `(4)` Product of the constant terms of `(x-1)(x^(2)-2)(x^(5)-5)=-10` `(5)` Product of the constant terms of `(x-1)(x^(3)-3)(x^(4)-4)=-12` Required coefficient `=7+12+15-10-12-8` `=34-30=4` |
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